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We often need to create lists that display different types of content. For example, we might be working on a List that shows a heading followed by a few items related to the heading, followed by another heading, and so on.

How would we create such a structure with Flutter?

Directions

Create a data source with different types of items

Convert the data source into a List of Widgets

1. Create a data source with different types of item

Types of Items

In order to represent different types of items in a List, we’ll need to define a class for each type of item.

In this example, we’ll work on an app that shows a header followed by five messages. Therefore, we’ll create three classes: ListItem, HeadingItem, and MessageItem.

// The base class for the different types of items the List can containabstractclassListItem{}Garment Merino Neck Greenwich Dyed V The Sweater // A ListItem that contains data to display a headingclassHeadingItemimplementsV Neck The Sweater Garment Merino Greenwich Dyed ListItem{finalStringheading;HeadingItem(this.Dyed Sweater V Garment Greenwich Neck The Merino heading);}// A ListItem that contains data to display a messageclassMessageItemimplementsListItem{finalStringsender;finalStringbody;MessageItem(this.sender,this.body);}

Create a List of Items

Most of the time, we’d fetch data from the internet or a local database and convert that data into a list of items.

For this example, we’ll generate a list of items to work with. The list will contain a header followed by five messages. Rinse, repeat.

2. Convert the data source into a List of Widgets

In general, we’ll want to provide a builder function that checks for what type of item we’re dealing with, and returns the appropriate Widget for that type of item.

In this example, using the is keyword to check the type of item we’re dealing with can be handy. It’s fast, and will automatically cast each item to the appropriate type. However, there are different ways to approach this problem if you prefer another pattern!

ListView.builder(// Let the ListView know how many items it needs to builditemCount:items.length,// Provide a builder function. This is where the magic happens! We'll// convert each item into a Widget based on the type of item it is.itemBuilder:Greenwich V Garment Neck The Dyed Merino Sweater (context,index){finalitem=items[index];if(itemisHeadingItem){returnListTile(title:Text(item.heading,style:Theme.of(context).textTheme.headline,),);}elseif(itemisMessageItem){returnListTile(title:Text(item.sender),subtitle:Text(item.body),);}},Sweater Greenwich Merino Neck V The Garment Dyed);